1. Field of the Invention
The present invention relates to devices used for sealing off wells, such as those producing oil or gas in the event of a blowout.
2. Description of the Prior Art
Presently, well heads are provided with mechanical blowout preventers of the sleeve-type and/or of the double ram type which are operated by hydraulic controls. However, due to human and mechanical failure, these preventers are not always operated in time to prevent the blowout and, unfortunately, uncontrolled eruptions of gas and oil are still occurring. Therefore, devices are needed which will stop a blowout after it has occurred.
U.S. Pat. No. 3,885,629 to Erb discloses just such a device. Here, the well head is tapped into and a branch line connected to supply liquid carbon dioxide or nitrogen under pressure. When a blowout occurs, a valve is opened which allows the carbon dioxide or nitrogen to mix with the fluid in the pipe. This produces a freezing of the liquid and thus stops the blowout. U.S. Pat. No. 3,738,424 to Osmun et al. also shows a similar freezing technique. Here a special freeze joint is incorporated in the piping. Two valves are supplied, one at the top of the freeze joint and one at the bottom of the freeze joint, and a refrigerant is circulated through the freeze joint by use of these valves. By this means, the fluid in the pipe is frozen and the blowout can be controlled.
Other prior art which demonstrates cooling of well pipes include U.S. Pat. No. 3,811,510 Rogers et al. which discloses the cooling of well fluids prior to the passage to a pump, whereby pumping efficiency can be increased. Also, U.S. Pat. No. 3,989,108 to Allen demonstrates a method for preventing water from entering a well in communication with a subterranean hydrocarbon reservoir by injecting a cold fluid which freezes the water forming ice barrier of the fluid flow. U.S. Pat. No. 2,929,451 to Hurlstone et al discloses a method and apparatus for freeing paraffin and asphalt and other obstructions in oil wells, and the like, by forcing heated fluid through a tube to melt the obstructing material.